The present invention relates to the construction of fixing a flexible sheet on to a chassis with electronic devices such as a portable telephone, etc.
A portable telephone, as shown in FIG. 5, generally comprises an upper case and a lower case which form a flat housing. A circuit board unit is accommodated in the housing. Disposed on a circuit board unit is a chassis having a flexible sheet made from synthetic resin mounted thereon, as shown in FIG. 6. A plurality of flexible switches are formed on the flexible sheet. The elasticity of the flexible sheet enables the user to turn on/off the flexible switch. A pair of terminals are closed or opened by the on/off manipulation.
FIG. 8(a) shows that the flexible sheet is electrically connected to a circuit board provided below the chassis. Respective manual buttons, as shown in FIG. 5, arranged above flexible switches are inserted into holes provided with the upper case in corresponding to a position of each flexible switch, whereby the manual buttons can be depressed externally from the case.
A liquid crystal panel is also disposed on the chassis, and fitted to an opening provided with the upper case in corresponding to a position for fixing the panel. The display of the panel can be viewed externally from the case through a transparent resin cover covering the opening. An antenna and an RF circuit are provided on the lower case.
A flexible sheet comprises, as shown in FIG. 7, a flat plate portion on which a plurality of flexible switches are arranged and a flat cable portion which has a terminal portion to be connected to a connector on the circuit board. FIG. 8(a) shows that the flat plate portion is in close contact with a surface of the chassis, and the flat cable portion is folded on a side of the chassis to have the portion connected to a connector on the circuit board disposed below the chassis.
The flat plate portion on the flexible sheet is so designed as to be in close contact with the chassis, as stated above. As shown in FIG. 8(a), the flat cable portion of the flexible sheet is folded back to have the terminal portion inserted into the connector on the circuit board, so that there arises the problem that a part of the flexible sheet is lifted up from the chassis, as shown in FIG. 8(b).
Portable telephones have been made compact and reduced in weight in recent years and an interior of a case is reduced in space. The flexible sheet is, therefore, liable to interfere with interior constructs. Since a part of the flexible sheet is lifted up as shown in FIG. 8(b) to produce reaction force and clearance, the problems are encountered that when an user depresses a manual button to function integrally with a flexible switch, he feels a dull click, or that a switch is positioned in an oblique direction to have the switch locked and not returned, or that when an user depresses a switch, noise is produced by the interference with the surrounding parts.
In view of the foregoing problems the present invention provides an electronic device comprising a case which is formed with a plurality of through holes, a chassis which is accommodated in an interior of the case, a flexible sheet which is mounted on the surface of the chassis and has a plurality of flexible switches arranged thereon, a circuit board which is disposed below the chassis and has a connector installed thereon, and a plurality of manual buttons which are disposed above respective flexible switches and project outwardly of a case through the through holes of the case. The flexible sheet has a flat plate portion to be in close contact with the chassis and a flat cable portion which extends on the edge of the flat plate portion and provided with a connecting terminal portion on its end. The flat cable portion is folded back toward the chassis to cause the connecting terminal portion to connect to the connector. The chassis is formed with a lift-up prevention piece for preventing a part of the flat plate portion of the flexible sheet from being lifted up from a surface of the chassis.
With the construction of fixing the flexible sheet, a lift-up prevention piece holds the flat cable portion of the flexible sheet, preventing a part of the flexible sheet from being lifted up.
The lift-up prevention piece, for example, has a through hole into which the flat cable portion of the flexible sheet is inserted, holding the flat cable portion of the flexible sheet.
The lift-up prevention piece is alternatively formed into a shape of hook to hook the flat cable portion of the flexible sheet, holding the flat cable portion of the flexible sheet.
The present invention is adapted to restrain a part of the flexible sheet from being lifted up, whereby the faulty action including dull click of the flexible switch and locking resulted from the reaction force or clearance caused by the lift-up.